1). Field of the Invention
The present invention relates to a tip for trapping nucleic acid capable of separating a nucleic acid component or plasmid DNA from a nucleic acid-containing sample such as a vital sample, a structural element encased in the tip and a process for forming the structural element.
2). Related Art
The conventional process for separating nucleic acid from a vital sample, etc. containing nucleic acid includes, for example, a process comprising at first allowing a surfactant to act upon a vital sample, etc. in the presence of protease, thereby liberating nucleic acid and then mixing the sample with phenol (and chloroform), followed by several runs of centrifugal separation of the mixture into an aqueous layer and an organic layer and recovery of nucleic acid in the form of sediments from the aqueous layer, and a column chromatographic process using a structural element comprising a specific single species of particles such as silicon oxide, etc. filled in a column. To simplify these processes, various attempts to improve the processes and apparatuses have been so far made.
JP-A-9-47278 discloses a process and an apparatus for DNA extraction and purification capable of extracting DNA from a culture solution at a low cost in a fully automatic manner, where the tip for the apparatus is in a vertical double structure of a first filter tube comprising a trap filler and a membrane filter and a second filter tube comprising a glass fiber filter, a glass powder layer and a membrane filter, and DNA extraction is carried out by a series of removal of impurities by filtration, DNA adsorption, washing and elution, using a vacuum means (pump).
Centrifugal separation of nucleic acid inevitably makes the scale of the apparatus larger and still involves a problem of damaging of nucleic acid per se due to the high speed revolution.
In case of filling a specific single species of particles in a column as in the column chromatography or in the tip of the above-mentioned reference, the particles take a closest packed structure due to the nature of fine particles (particularly when the particle sizes are uniform), or in case that there is some particle size distribution, smaller particles gather and enter between larger particles to form a compact state, thereby deteriorating the liquid passage therethrough, consequently requiring much time for the sample passage. When a vacuum pump is used to shorten the sample passage time in the separation, the same problem as in the centrifugal separation, i.e. breaking of nucleic acid, is encountered.